What's best for the tree should also be considered. Most traditional bonsai trees are from specimens native to temperate climates that won't do well for extended periods indoors. They need more light than is typically provided and need a cold dormant period for optimum health. They're best kept outside, with the occasional brief visit indoors if you want to use them as part of a display.

There are some tropical varieties that do get bonsai'd for indoor use. I've seen this done to Jade plants for example. I've always had bad experiences with Jades being infested with insects, but their natural sturdy branching makes me want to try one in a treefrog tank (not-bonsai'd though, just shaped to the tank).

What kind of frogs are you looking to get plants for?